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=============================================================================
FreeBSD-EN-20:03.sshd                                           Errata Notice
                                                          The FreeBSD Project

Topic:          Misleading log messages upon successful sshd login

Category:       contrib
Module:         sshd
Announced:      2020-03-19
Affects:        FreeBSD 12.1
Corrected:      2019-11-28 02:18:19 UTC (stable/12, 12.1-STABLE)
                2020-03-19 16:34:11 UTC (releng/12.1, 12.1-RELEASE-p3)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

The sshd server implements the secure shell protocol, providing remote
access.

II.  Problem Description

Due to a programming error, error messages of the form "Failed unknown for
user <user> ..." will be emitted to auth.log for successful logins.

III. Impact

Log files will be confusing, and programs like fail2ban that parse logs will
not function correctly.

IV.  Workaround

No workaround is available.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date, and restart the sshd
service.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# nohup service sshd restart

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-20:03/sshd.patch
# fetch https://security.FreeBSD.org/patches/EN-20:03/sshd.patch.asc
# gpg --verify sshd.patch.asc

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart the applicable daemons, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r355160
releng/12.1/                                                      r359134
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=234793>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-20:03.sshd.asc>
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